Check if device exists

src/freedombone-notification

@@ -76,21 +76,19 @@ if [ ! "$ADMIN_EMAIL_ADDRESS" ]; then
     ADMIN_EMAIL_ADDRESS=${ADMIN_USERNAME}@${HOSTNAME}
 fi
 
-canary_subject=$'USB canary'
 notification_image_filename=/tmp/notification.jpg
-image_extra=''
-if [[ "$SUBJECT" == *"$canary_subject"* ]]; then
+if [[ "$SUBJECT" == *"USB"* ]]; then
     if [ -f /usr/bin/fswebcam ]; then
         # Preferentially use a secondary camera which can
         # be set up from an appropriate viewing angle
-        if [ -f /dev/video1 ]; then
+        if [ -e /dev/video1 ]; then
             if [ -f $notification_image_filename ]; then
                 rm $notification_image_filename
             fi
             fswebcam -d /dev/video1 --jpeg 50 -D 1 $notification_image_filename
         else
             # Otherwise use the built-in camera
-            if [ -f /dev/video0 ]; then
+            if [ -e /dev/video0 ]; then
                 if [ -f $notification_image_filename ]; then
                     rm $notification_image_filename
                 fi
@@ -99,7 +97,10 @@ if [[ "$SUBJECT" == *"$canary_subject"* ]]; then
         fi
     fi
 fi
+
+image_extra=''
 if [ -f $notification_image_filename ]; then
+    # extra option for mail command
     image_extra="-A $notification_image_filename"
 
     # If syncthing is installed then copy the image to the admin